External SONY DVD writer cannot burn CD-R, but burns CD-RW, why ??

[batcher1]

I have a External DVD writer - SONY DVD RW DRU-820A plugged into USB. Bought 1 year before. So far no problem at all. Just 1 week before i got a problem.
My problem is when i burning whatever files such as video,audio,data's into CD-R disc, the software[nero 6] hangs up and not responding to burn into CD-R disc and also not burning DVD blank disc. If i burn those files in CD-RW blank disc, it burns, no problem at all.

The problem that i face was why my DVD writer is not burning into CD-R and DVD, and burns only in CD-RW disc.
Isn't any software driver and windows system files problem that doesn't burn in CD-R and DVD's.
Just 1 week only this kind of problem comes in my DVD writer.

My PC configuration is :
Intel 865 GBF motherboard,
512 MB RAM,
Windows XP Professional with Service Pack 2

Pleae help me to solve this problem,
Thanking you sincerely.

[batcher1]

Please help me to solve this problem.

I have tried re-installed the Nero software and tried in another burning software in Roxio Easy CD creator, the same problem comes when burning in CD-R,DVD ,not in CD-RW disc.

[shoarthing]

 . .  since it is portable, please try it attached to another PC - this will short-circuit some of the diagnostics.